JP2020109190A - Fibrous cellulose, fibrous cellulose-containing material, formed body, and method for producing fibrous cellulose - Google Patents

Abstract

To provide, on one hand, a fibrous cellulose in which yellowing of a fine fibrous cellulose having phosphite group is suppressed, and, on the other hand, a composition obtained using the fine fibrous cellulose in which the transparency is increased.SOLUTION: The present invention relates to a fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorus oxo acid group or a substituent derived from the phosphorus oxo acid group, and in which, setting the first dissociated acid amount in the fibrous cellulose as A1 and the total dissociated acid amount in the fibrous cellulose as A2, A1 is 1.35 mmol/g or more, and the value of A1/A2 is 0.51 or more, and when a sheet is formed under a predetermined condition, the YI value of the sheet is 6.0 or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to fibrous cellulose, a fibrous cellulose-containing material, a molded article, and a method for producing fibrous cellulose.

Conventionally, cellulose fibers have been widely used in clothing, absorbent articles, paper products and the like. As cellulose fibers, in addition to fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, fine fibrous cellulose having a fiber diameter of 1 μm or less is known. Fine fibrous cellulose has been attracting attention as a new material, and its uses are diverse. For example, the development of sheets, resin composites and thickeners containing fine fibrous cellulose is under way.

The fine fibrous cellulose can be produced by mechanically treating conventional cellulose fibers, but the cellulose fibers are strongly bonded by hydrogen bonds. Therefore, enormous energy is required to obtain fine fibrous cellulose simply by performing mechanical treatment. It is known that pretreatment such as chemical treatment or biological treatment is effective in addition to mechanical treatment in order to produce fine fibrous cellulose with smaller mechanical treatment energy. In particular, when a hydrophilic functional group (for example, a carboxy group, a cation group, a phosphate group, etc.) is introduced into the hydroxy group on the surface of cellulose by chemical treatment, electric repulsion between the ions occurs and the ions are hydrated. By doing so, the dispersibility in an aqueous solvent is remarkably improved. Therefore, the energy efficiency of miniaturization is higher than that in the case where no chemical treatment is applied.

For example, Patent Document 1 discloses a method for producing fine fibrous cellulose, which has a step of treating a fiber raw material containing cellulose with at least one compound selected from phosphorus oxo acids or salts thereof, and a step of defibrating treatment. It is disclosed. Further, in Patent Document 2, a compound having a phosphoric acid group or/and a salt thereof is allowed to act on a fiber raw material containing cellulose in the presence of urea or/and a derivative thereof to introduce a phosphoric acid group into the fiber raw material. Disclosed is a method for producing phosphoric acid esterified fine cellulose fibers, which comprises a step and a step of subjecting to a refinement treatment.

In Patent Document 3, an additive (A) composed of at least one of phosphorous acid and a metal salt of phosphorous acid and an additive (B) composed of at least one of urea and a urea derivative are added to a cellulose fiber. A method for producing a cellulose fine fiber which is defibrated after being added, heated and washed is disclosed.

JP, 2013-127141, A International Publication No. 2014/185505 International Publication No. 2018/159473

As described above, fine fibrous cellulose having a phosphorus oxo acid group is known. Here, when the present inventors proceeded with the study on the fine fibrous cellulose having a phosphite group, when the phosphorus oxo oxidation treatment time was lengthened in order to introduce many phosphorus oxo acid groups containing a phosphite group, It was found that unintended elimination of the phosphite group may occur or that the fine fibrous cellulose having the phosphite group may yellow. And, in the composition obtained by using such fine fibrous cellulose, there was a tendency that the transparency was lowered.

Therefore, the present inventors, in order to solve the problems of such conventional techniques, while suppressing the yellowing of the fine fibrous cellulose having a phosphite group, a composition obtained by using the fine fibrous cellulose The study was advanced with the aim of increasing transparency.

As a result of earnest studies to solve the above problems, the present inventors have carried out phosphorus oxo oxidation treatment a plurality of times in the production process of fine fibrous cellulose, and decomposed urea and/or urea derivative in each treatment process. By controlling the ratio to be a predetermined value or less, it has succeeded in increasing the transparency of the composition obtained by using the fine fibrous cellulose while suppressing the yellowing of the fine fibrous cellulose having a phosphite group.
Specifically, the present invention has the following configurations.

[1] A fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group,
When the first dissociated acid amount in the fibrous cellulose is A1 and the total dissociated acid amount in the fibrous cellulose is A2, A1 is 1.35 mmol/g or more and the value of A1/A2 is 0.51 or more. Yes,
Fibrous cellulose having a YI value of 6.0 or less when the sheet is formed under the following condition (a);
Condition (a):
A fibrous cellulose dispersion having a solid content concentration of 0.5% by mass was prepared, and 20 parts by mass of an aqueous polyethylene oxide solution having a concentration of 0.5% by mass was added to 100 parts by mass of the fibrous cellulose dispersion, followed by coating. A coating solution is applied onto a substrate to form a sheet having a basis weight of 50 g/m ² .
[2] A fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorous acid group or a substituent derived from a phosphorous acid group,
The introduced amount of the phosphite group or the substituent derived from the phosphite group is 1.35 mmol/g or more,
Fibrous cellulose having a YI value of 6.0 or less when the sheet is formed under the following condition (a);
Condition (a):
A fibrous cellulose dispersion having a solid content concentration of 0.5% by mass was prepared, and 20 parts by mass of an aqueous polyethylene oxide solution having a concentration of 0.5% by mass was added to 100 parts by mass of the fibrous cellulose dispersion, followed by coating. A coating solution is applied onto a substrate to form a sheet having a basis weight of 50 g/m ² .
[3] The fibrous cellulose according to [1] or [2], which has a YI value of 3.0 or less when the sheet is formed under the condition (a).
[4] The fibrous cellulose according to any one of [1] to [3], which has a YI value of 1.5 or less when the sheet is formed under the condition (a).
[5] A fibrous cellulose-containing composition containing the fibrous cellulose according to any one of [1] to [4].
[6] The fibrous cellulose-containing composition according to [5], which contains a solvent.
[7] The fibrous cellulose-containing composition according to [6], wherein the solvent is water and the total light transmittance is 80% or more when the solid content concentration is 0.2% by mass.
[8] A molded product formed from the fibrous cellulose according to any one of [1] to [4] or the fibrous cellulose-containing composition according to any one of [5] to [7].
[9] The molded product according to [8], which is in the form of a sheet.
[10] A fibrous cellulose having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, wherein the first dissociated acid amount in the fibrous cellulose is A1′ and the total dissociated acid amount in the fibrous cellulose is A2′. When this is done, fibrous cellulose having A1′ of 1.35 mmol/g or more, A1′/A2′ value of 0.51 or more, and a degree of polymerization of 500 or more.
[11] A fibrous cellulose having a phosphorous acid group or a substituent derived from a phosphorous acid group, wherein the introduction amount of the phosphorous acid group or a substituent derived from a phosphorous acid group is 1.35 mmol/g or more. And a fibrous cellulose having a degree of polymerization of 500 or more.
[12] A step of mixing a cellulose raw material with phosphorus oxo acid and/or a salt thereof and urea and/or a urea derivative to obtain a cellulose raw material having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group. A method for producing fibrous cellulose,
The step of obtaining a cellulose raw material having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group is one cycle in which the cellulose raw material is mixed with phosphorus oxo acid and/or a salt thereof and urea and/or a urea derivative and heated. Including multiple steps,
The decomposition rate of urea and/or urea derivative in one cycle process is 95% or less,
A method for producing fibrous cellulose, wherein A1/A2 is 0.51 or more, where A1 is the first dissociated acid amount in the fibrous cellulose and A2 is the total dissociated acid amount in the fibrous cellulose.
[13] Cellulose having a phosphorous acid group or a substituent derived from a phosphorous acid group obtained by mixing a compound having a phosphorous acid group and/or a salt thereof and urea and/or a urea derivative with a cellulose raw material. A method for producing fibrous cellulose, which comprises the step of obtaining a raw material,
In the step of obtaining a phosphorous acid group or a substituent cellulose raw material derived from a phosphorous acid group, the cellulose raw material is mixed with a compound having a phosphorous acid group and/or a salt thereof, and urea and/or a urea derivative. , Including a plurality of one cycle steps of heating,
A method for producing fibrous cellulose, wherein the decomposition rate of urea and/or urea derivative in one cycle step is 95% or less.

ADVANTAGE OF THE INVENTION According to this invention, the transparency of the composition obtained using the said fine fibrous cellulose can be improved, suppressing the yellowing of the fine fibrous cellulose which has a phosphite group.

FIG. 1 is a graph showing the relationship between the dropping amount of NaOH and pH for a slurry containing fibrous cellulose having a phosphorous acid group.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments or specific examples, but the present invention is not limited to such embodiments.

(Fibrous cellulose)
A first aspect of the present invention relates to a fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorus oxo acid group or a substituent derived from the phosphorus oxo acid group. Here, when the first dissociated acid amount in the fibrous cellulose is A1 and the total dissociated acid amount in the fibrous cellulose is A2, A1 is 1.35 mmol/g or more and the value of A1/A2 is 0. It is 51 or more. Furthermore, when a sheet is formed under the following condition (a), the YI value of the sheet becomes 6.0 or less.
Condition (a):
A fibrous cellulose dispersion having a solid content concentration of 0.5% by mass was prepared, and 20 parts by mass of an aqueous polyethylene oxide solution having a concentration of 0.5% by mass was added to 100 parts by mass of the fibrous cellulose dispersion, followed by coating. A coating solution is applied onto a substrate to form a sheet having a basis weight of 50 g/m ² .

A second aspect of the present invention relates to a fibrous cellulose having a fiber width of 1000 nm or less and having a phosphite group or a substituent derived from the phosphite group. Here, the introduction amount of the phosphite group or the substituent derived from the phosphite group is 1.35 mmol/g or more, and when the sheet is formed under the above condition (a), the YI value of the sheet is 6. It becomes 0 or less. In the present specification, the phosphorous acid group or the substituent derived from the phosphorous acid group may be simply referred to as a phosphorous acid group.

Since the fibrous cellulose of the present invention has the above-mentioned constitution, transparency of a composition obtained by using the fine fibrous cellulose while suppressing yellowing of the fine fibrous cellulose having a phosphite group Can be increased. For example, when a molded product such as a sheet is formed by using fine fibrous cellulose having a phosphite group, heat is applied in the molding process. As a result, a molded product with less yellowing can be obtained. In addition, the transparency of the dispersion or molded product containing such fine fibrous cellulose can be improved.

Usually, when it is attempted to improve the transparency of a dispersion liquid containing fine fibrous cellulose, the degree of fiber disintegration is increased by introducing many anionic groups such as phosphite groups. Here, when trying to introduce the phosphite group into the fibrous cellulose, it is conceivable that the phosphoroxo oxidation treatment time is lengthened, but in such a case, desorption of the phosphite group proceeds conversely. The present inventors have found that there are cases. Further, it was confirmed that the fibrous cellulose turned yellow when the phosphorus oxo oxidation treatment time was prolonged, and the transparency of the composition containing the fine fibrous cellulose tended to decrease. Therefore, in the present invention, rather than simply extending the phosphorus oxo oxidation treatment time, the phosphorus oxo acid group introduction step is performed multiple times, and further, by appropriately controlling the urea decomposition rate at each time, the phosphorous acid in the fibrous cellulose is increased. It was decided to increase the amount of introduced groups. When such a production method is adopted, the introduction amount of the phosphite group can be increased, and the yellowing of the fibrous cellulose can be suppressed. Further, since the introduction amount of the phosphite group can be increased, the transparency of the composition containing fine fibrous cellulose is also improved.

When the sheet is formed under the above condition (a), the YI value of the sheet may be 6.0 or less, preferably 4.5 or less, more preferably 3.0 or less, and 1. It is more preferably 5 or less. The lower limit of the YI value of the sheet is not particularly limited and may be 0.0. The YI value of the sheet is a value measured according to JIS K7373. As the measuring device, for example, Color Cute i manufactured by Suga Test Instruments Co., Ltd. can be used.

When the fibrous cellulose of the present invention is dispersed in water to obtain a dispersion having a solid content concentration of 0.2% by mass, the total light transmittance of the dispersion is preferably 80% or more, and 90% or more. Is more preferable, 95% or more is still more preferable, and 98% or more is particularly preferable. Here, the total light transmittance of the dispersion liquid is a value measured according to JIS K7361. The total light transmittance of the dispersion is measured using a haze meter. At this time, a glass cell for liquid having an optical path length of 1 cm is used. The zero point measurement is performed with ion-exchanged water contained in the glass cell. Before the measurement, the dispersion liquid is allowed to stand for 24 hours in an environment of 23° C. and a relative humidity of 50% so that the liquid temperature of the dispersion liquid is 23° C.

The present invention may be related to fibrous cellulose having a fiber width of more than 1000 nm. A third aspect of the present invention is a fibrous cellulose having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, wherein the first dissociation acid amount in the fibrous cellulose is A1′ and the total dissociation in the fibrous cellulose is When the acid amount is A2', A1' is 1.35 mmol/g or more, the value of A1'/A2' is 0.51 or more, and the degree of polymerization is 500 or more.

Further, a fourth aspect of the present invention is a fibrous cellulose having a phosphite group or a substituent derived from a phosphite group, the introduction of a phosphite group or a substituent derived from a phosphite group It relates to fibrous cellulose having an amount of 1.35 mmol/g or more and a degree of polymerization of 500 or more.

As described above, conventionally, when trying to enhance the transparency of a dispersion liquid or the like containing fine fibrous cellulose, it is possible to increase the defibration degree of the fibers by introducing a large amount of anionic groups such as phosphite groups. Has been done. Here, when trying to introduce a phosphite group into fibrous cellulose, it is conceivable to lengthen the phosphoroxo oxidation treatment time. However, the present inventors have found that in such a case, the degree of polymerization of the fibrous cellulose before miniaturization tends to decrease. Therefore, as a result of intensive studies, the inventors of the present invention carried out the phosphorus oxo acid group introduction step multiple times, and further, by appropriately controlling the urea decomposition rate at each time, the degree of polymerization of the fibrous cellulose before miniaturization. Succeeded in suppressing the decrease of. As a result, they have found that the yellowing of the obtained fibrous cellulose is suppressed. Further, it has been found that when the fibrous cellulose is miniaturized, yellowing of the fine fibrous cellulose can be more effectively suppressed, and the transparency of the composition containing the fine fibrous cellulose can be further enhanced.

The degree of polymerization of the fibrous cellulose before micronization is preferably 500 or more, more preferably 550 or more, and further preferably 600 or more. The degree of polymerization of fibrous cellulose is preferably 2000 or less. By setting the degree of polymerization of the fibrous cellulose before micronization within the above range, when the micronized fine fibrous cellulose is dispersed in a dispersion medium to prepare a dispersion liquid, a highly transparent dispersion liquid is easily obtained. Become. Moreover, when a sheet is formed from a dispersion liquid containing fine fibrous cellulose, a sheet having a low YI value is easily obtained. The fibrous cellulose before being micronized is, for example, fibrous cellulose having a fiber width of more than 1000 nm.

The degree of polymerization of fibrous cellulose is a value calculated from the pulp viscosity measured according to Tappi T230. Specifically, the fibrous cellulose to be measured is dispersed in an aqueous solution of copper ethylenediamine to obtain a viscosity (η1) and a blank viscosity (η0) measured only with a dispersion medium, and then a specific viscosity is measured. (Ηsp) and intrinsic viscosity ([η]) are measured according to the following formulas.
ηsp=(η1/η0)-1
[Η]=ηsp/(c(1+0.28×ηsp))
Here, c in the formula represents the concentration of fibrous cellulose at the time of viscosity measurement.
Furthermore, the degree of polymerization (DP) is calculated from the following formula.
DP=1.75×[η]
Since this degree of polymerization is an average degree of polymerization measured by a viscosity method, it may be referred to as a “viscosity average degree of polymerization”.

In the first aspect and the second aspect of the present invention, the fiber width of the fibrous cellulose is 1000 nm or less. The fiber width of the fibrous cellulose is preferably 100 nm or less, more preferably 8 nm or less. Thereby, the dispersibility in the solvent can be more effectively enhanced. In the present specification, fibrous cellulose having a fiber width of 1000 nm or less may be referred to as fine fibrous cellulose.

In the third and fourth aspects of the invention, the average fiber width of the fibrous cellulose may be greater than 1000 nm. In this case, the fiber width of the fibrous cellulose is preferably 50 μm or less, more preferably 40 μm or less, and further preferably 30 μm or less.

The fiber width of the fibrous cellulose can be measured by, for example, observation with an electron microscope. The average fiber width of the fibrous cellulose may be larger than 1000 nm or 1000 nm or less. For example, when the average fiber width of the fibrous cellulose is greater than 1000 nm, it is preferably greater than 1 μm and less than or equal to 50 μm, more preferably greater than 1 μm and less than or equal to 40 μm, and even more preferably greater than 1 μm and less than or equal to 30 μm. .. When the average fiber width of the fibrous cellulose is 1000 nm or less, it is preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more. Particularly preferably, it is 10 nm or less. The fibrous cellulose is, for example, monofilament cellulose.

The average fiber width of the fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and the suspension is cast on a hydrophilized carbon film-coated grid to obtain a TEM observation sample. And When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Then, observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times or 50000 times according to the width of the fiber to be observed. However, the sample, observation conditions and magnification are adjusted so as to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary position in the observed image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber intersecting the straight line X and the straight line Y is visually read from the observed image satisfying the above conditions. In this way, at least three sets of observation images of surface portions that do not overlap each other are obtained. Then, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. Thereby, the fiber width of at least 20 fibers×2×3=120 fibers is read. Then, the average value of the read fiber width is set as the average fiber width of the fibrous cellulose.

The fiber length of the fibrous cellulose is not particularly limited, but when the fiber width is larger than 1000 nm, the fiber length is preferably 0.1 mm or more, more preferably 0.6 mm or more. Further, the fiber length is preferably 50 mm or less, more preferably 20 mm or less. When the fiber width is 1000 nm or less, the fiber length is preferably 0.1 μm or more. The fiber length is preferably 1000 μm or less, more preferably 800 μm or less, and further preferably 600 μm or less. By setting the fiber length within the above range, breakage of the crystalline region of the fibrous cellulose can be suppressed. It is also possible to set the slurry viscosity of the fibrous cellulose within an appropriate range. The fiber length of the fibrous cellulose can be determined by image analysis using TEM, SEM, or AFM, for example.

The fibrous cellulose preferably has a type I crystal structure. Here, the fact that the fibrous cellulose has an I-type crystal structure can be identified in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ=1.5418Å) monochromated with graphite. Specifically, it can be identified by having typical peaks at two positions near 2θ=14° or more and 17° or less and around 2θ=22° or more and 23° or less. The proportion of the I-type crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. Thereby, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion coefficient. The crystallinity is obtained by measuring an X-ray diffraction profile and using the pattern according to a conventional method (Seagal et al., Textile Research Journal, Vol. 29, page 786, 1959).

The axial ratio (fiber length/fiber width) of the fibrous cellulose is not particularly limited, but is preferably 20 or more and 10000 or less, and more preferably 50 or more and 1000 or less. By setting the axial ratio to the above lower limit or more, it is easy to form a sheet containing fine fibrous cellulose. By setting the axial ratio to be equal to or less than the above upper limit, for example, when handling fibrous cellulose as a dispersion liquid, handling such as dilution becomes easy, which is preferable.

The fibrous cellulose in this embodiment has both a crystalline region and an amorphous region, for example. In particular, fine fibrous cellulose having both a crystalline region and an amorphous region and a high axial ratio is realized by the method for producing fine fibrous cellulose described below.

Fibrous cellulose has a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group (sometimes referred to simply as a phosphorus oxo acid group). The substituent derived from the phosphorus oxo acid group includes a substituent such as a salt of the phosphorus oxo acid group and a phosphorus oxo acid ester group.

The amount of phosphorus oxo acid group introduced into the fibrous cellulose can be measured, for example, by the neutralization titration method. In the measurement by the neutralization titration method, the introduced amount is measured by determining the pH change while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fibrous cellulose.

FIG. 1 is a graph showing the relationship between the dropping amount of NaOH and pH for a slurry containing fibrous cellulose having a phosphorous acid group. The amount of phosphorus oxo acid group introduced into the fibrous cellulose is measured, for example, as follows.
When the fibrous cellulose to be measured is the fibrous cellulose before micronization, first, the fibrous cellulose is subjected to an acid treatment. In the acid treatment of fibrous cellulose, the fibrous cellulose is diluted with ion-exchanged water so that the content becomes 2% by mass, and a sufficient amount of 1N hydrochloric acid aqueous solution is added little by little while stirring. Next, this pulp suspension is stirred for 15 minutes and then dehydrated to obtain a dehydrated sheet, which is diluted again with ion-exchanged water, and 1000 parts of 1N hydrochloric acid aqueous solution is added to 100 parts by mass of fibrous cellulose (absolute dry mass). Add parts by mass. By repeating this operation 5 times, the phosphorus oxo acid group contained in the fibrous cellulose is completely converted to the acid form. Further, the pulp suspension is stirred and uniformly dispersed, and then filtered and dehydrated to obtain a dehydrated sheet. By repeating the operation, excess hydrochloric acid is sufficiently washed out. Then, the obtained acid-type fibrous cellulose is diluted to a content of 0.2 mass% to prepare a suspension. If necessary, after the acid treatment, a defibration treatment similar to the defibration treatment step described below may be performed on the measurement target. The obtained suspension is subjected to neutralization titration with an alkali described later.
When the fibrous cellulose to be measured is fine fibrous cellulose, first, a slurry containing fine fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, a defibration process similar to the defibration process step described below may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin. The slurry treated with the strongly acidic ion exchange resin is subjected to neutralization titration with an alkali described below.
In the neutralization titration with alkali, the pH change is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in the upper part of FIG. 1 is obtained. In the titration curve shown in the upper part of FIG. 1, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of FIG. 1, the pH is plotted against the amount of alkali added. The increment (differential value) (1/mmol) is plotted. In this neutralization titration, two points at which the increment (the differential value of pH with respect to the amount of alkali added) is maximized are confirmed in the curve plotting the pH measured with respect to the amount of alkali added. Among these, the maximum point of the increment obtained first after adding alkali is referred to as a first end point, and the maximum point of the increment obtained next is referred to as a second end point. The amount of alkali required from the start of titration to the first end point becomes equal to the amount of the first dissociated acid of fibrous cellulose contained in the slurry used for the titration, and the alkali amount required from the first end point to the second end point. The amount becomes equal to the amount of the second dissociated acid of the fibrous cellulose contained in the slurry used for the titration, and the amount of alkali required from the start of the titration to the second end point becomes the total amount of the dissociated acid in the slurry used for the titration. Will be equal. The value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated is the phosphorus oxo acid group introduction amount (mmol/g). In addition, when simply saying the phosphorus oxo acid group introduction amount (or phosphorus oxo acid group amount), it means the first dissociation acid amount.
In FIG. 1, the region from the start of titration to the first end point is called the first region, and the region from the first end point to the second end point is called the second region. For example, when the phosphorous acid group is a phosphoric acid group and the phosphoric acid group causes condensation, the amount of the weakly acidic group in the phosphorous acid group (also referred to as the amount of the second dissociated acid in the present specification) is apparent. As a result, the amount of alkali required for the second region decreases compared to the amount of alkali required for the first region. On the other hand, the amount of the strongly acidic group in the phosphorus oxo acid group (also referred to as the amount of the first dissociated acid in the present specification) matches the amount of phosphorus atoms regardless of the presence or absence of condensation. When the phosphorous acid group is a phosphorous acid group, the weak acid group does not exist in the phosphorous acid group, so that the alkali amount required for the second region is reduced or the alkali amount required for the second region is reduced. May be zero. In this case, there is only one point in the titration curve where the pH increment becomes maximum.

In the measurement of the amount of phosphorus oxo acid group by the titration method, an accurate value such as a lower amount of phosphorus oxo acid group than originally should be obtained when the amount of one drop of the aqueous sodium hydroxide solution is too large or the titration interval is too short. Sometimes you can't get it. As an appropriate dropping amount and titration interval, for example, it is desirable to titrate 0.1N sodium hydroxide aqueous solution by 10 to 50 μL in 5 to 30 seconds. In order to eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, it is desirable to measure while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration to the end of titration.

In the first aspect of the present invention, when the first dissociated acid amount (mmol/g) in the fibrous cellulose is A1 and the total dissociated acid amount (mmol/g) in the fibrous cellulose is A2, A1 is 1 It may be 0.35 mmol/g or more, preferably 1.50 mmol/g or more, more preferably 1.75 mmol/g or more, and further preferably 2.00 mmol/g or more. Further, A1 is preferably 5.20 mmol/g or less, more preferably 3.65 mmol/g or less, and further preferably 3.00 mmol/g or less. In the present specification, A1 has the same meaning as the phosphorus oxo acid group introduction amount or the phosphorus oxo acid group amount, so that the phosphorus oxo acid group introduction amount (or phosphorus oxo acid group amount) is also preferably within the above range. Here, the unit mmol/g indicates the amount of the substituent per 1 g of the mass of the fibrous cellulose when the counter ion of the phosphorus oxo acid group is a hydrogen ion (H ⁺ ). By setting the introduction amount (A1) of the phosphorus oxo acid group within the above range, it is possible to easily miniaturize the fiber raw material, and it is possible to enhance the stability of the fibrous cellulose. Further, by setting the introduction amount of the phosphorus oxo acid group within the above range, when the composition or sheet such as the dispersion liquid is formed, the composition or sheet can exhibit high transparency. The value of A1′ is also preferably within the above range.

In the first aspect of the present invention, the value of A1/A2 is preferably 0.51 or more, more preferably 0.64 or more, and further preferably 0.80 or more. Further, the upper limit value of A1/A2 is preferably 1.0. Here, the first dissociated acid amount (A1) in the fibrous cellulose is the amount of alkali (mmol) required from the start of titration to the first end point in the titration curve described above, and the solid content (g ) Divided by. That is, the first dissociated acid amount (A1) is a value obtained by dividing the substance amount (mmol) of the acid ionized and neutralized in the first step by the solid content (g) in the titration target slurry. The total amount of dissociated acid (A2) in the fibrous cellulose is a value obtained by dividing the amount of alkali (mmol) required from the start of titration to the second end point by the solid content (g) in the titration target slurry. That is, the total dissociated acid amount (A2) is a value obtained by dividing the substance amount (mmol) of all the acids that are ionized and neutralized in all stages by the solid content (g) in the titration target slurry. Therefore, as the value of A1/A2 is closer to 1, it means that the amount of weak acid (such as the amount of weakly acidic group in phosphorous acid group) is smaller. In the first aspect of the present invention, the transparency of the composition obtained by using the fine fibrous cellulose is suppressed while controlling the yellowing of the fine fibrous cellulose by setting the value of A1/A2 within the above range. Can be increased. The value of A1'/A2' is also preferably within the above range.

The value of A1/A2 approaches 1 in both cases where the phosphoric acid group is condensed and when the phosphorous acid group is present. As a method for determining whether the factor that A1/A2 approaches 1 is due to the condensation of a phosphoric acid group or the presence of a phosphorous acid group, for example, a condensed structure of phosphoric acid such as acid hydrolysis is used. Examples include a method of performing the above-mentioned titration operation after the treatment of cutting, a method of performing the above-mentioned titration operation after performing a treatment of converting a phosphite group into a phosphate group such as an oxidation treatment.

The phosphorus oxo acid group or the substituent derived from the phosphorus oxo acid group is, for example, a substituent represented by the following formula (1). The substituent derived from the phosphorus oxo acid group includes a substituent such as a salt of the phosphorus oxo acid group and a phosphorus oxo acid ester group. Further, the substituent derived from the phosphorus oxo acid group may be contained in the fibrous cellulose as a group condensed with the phosphorus oxo acid group (for example, a pyrophosphate group).

In the formula (1), a, b and n are natural numbers and m is an arbitrary number (provided that a=b×m). Of α ¹ , α ² ,..., α ⁿ and α′, a is O ⁻ , and the rest is either R or OR. Here, R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon group. It is a hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof. R may be a group derived from a cellulose molecular chain. Of these, either α ⁿ or α′ is preferably R, and R is particularly preferably a hydrogen atom. Further, n is preferably 1. That is, the phosphorous acid group is preferably a phosphorous acid group. The phosphite group may be a substituent derived from the phosphite group.

In the second aspect of the present invention, the fibrous cellulose has a phosphorous acid group or a substituent derived from a phosphorous acid group. That is, in the formula (1), a of α ⁿ and α′ is O ⁻ , and either α ⁿ or α′ is R. Above all, R is preferably a hydrogen atom.

Note that a part of the phosphorus oxo acid group or the substituent derived from the phosphorus oxo acid group may be a phosphoric acid group or a substituent derived from the phosphoric acid group, or a group in which the phosphorus oxo acid group is condensed (for example, pyrophosphoric acid Group). Thus, the fibrous cellulose is a phosphorous acid group or a substituent group derived from a phosphorous acid group (hereinafter, also simply referred to as a phosphorous acid group), and a substituent group derived from a phosphoric acid group or a phosphoric acid group (hereinafter , And also referred to as a phosphoric acid group) as a substituent, the proportion of the phosphorous acid group in the substituent represented by the formula (1) is preferably 10% by mass or more, and 20% by mass. % Or more, and more preferably 30% by mass or more.

Examples of the saturated-linear hydrocarbon group represented by R in the formula (1) include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group, but are not particularly limited. Examples of the saturated-branched hydrocarbon group include i-propyl group and t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include a cyclopentyl group and a cyclohexyl group, but are not particularly limited. Examples of the unsaturated-straight chain hydrocarbon group include a vinyl group and an allyl group, but are not particularly limited. Examples of the unsaturated-branched hydrocarbon group include, but are not limited to, i-propenyl group and 3-butenyl group. Examples of the unsaturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentenyl group and a cyclohexenyl group. Examples of the aromatic group include a phenyl group and a naphthyl group, but are not particularly limited.

Further, the derivative group in R is a functional group in which at least one of functional groups such as a carboxy group, a hydroxy group, or an amino group is added or substituted to the main chain or side chain of the above-mentioned various hydrocarbon groups. Examples thereof include groups, but are not particularly limited. Further, the number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R in the above range, the molecular weight of the phosphorus oxo acid group can be set in an appropriate range, the permeation into the fiber raw material is facilitated, and the yield of fine cellulose fibers is increased. You can also

β ^b+ is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or more cations composed of organic substances include aliphatic ammonium and aromatic ammonium, and examples of monovalent or more cations composed of inorganic substances include alkali metal ions such as sodium, potassium or lithium, Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions and the like, but are not particularly limited. These may be applied alone or in combination of two or more. As the cation having a valence of 1 or more consisting of an organic substance or an inorganic substance, sodium or potassium ions, which are less likely to yellow when the β-containing fiber raw material is heated and are industrially usable, are preferred, but are not particularly limited.

The fact that the fibrous cellulose has a phosphite group as a substituent means that the infrared absorption spectrum of the dispersion containing the fibrous cellulose was measured, and phosphon, which is a tautomer of the phosphite group, was found around 1210 cm ^-1. This can be confirmed by observing absorption based on P=O of the acid group. Further, the fibrous cellulose having a phosphite group as a substituent includes a method of confirming a chemical shift using NMR, and a method of combining various titration methods with elemental analysis.

The fibrous cellulose may have another anionic group in addition to the phosphorus oxo acid group or the substituent derived from the phosphorus oxo acid group. Examples of such an anionic group include a carboxy group originally contained in pulp.

(Method for producing fibrous cellulose)
The present invention relates to a method for producing fibrous cellulose. In the method for producing fibrous cellulose according to the first aspect of the present invention, when the first dissociated acid amount in fibrous cellulose is A1 and the total dissociated acid amount in fibrous cellulose is A2, the value of A1/A2 is 0. The method for producing fibrous cellulose is 0.51 or more. The production method according to the first aspect is a cellulose having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group obtained by mixing a cellulose raw material with a phosphorus oxo acid and/or a salt thereof and urea and/or a urea derivative. The process of obtaining a raw material is included. Then, in the step of obtaining a cellulose raw material having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, phosphorus oxo acid and/or its salt and urea and/or urea derivative are mixed and heated to the cellulose raw material. The decomposition rate of urea and/or urea derivative in one cycle process is 95% or less including a plurality of one cycle processes.

The method for producing fibrous cellulose according to the second aspect of the present invention is a method for producing fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorous acid group or a substituent derived from a phosphorous acid group. In the production method according to the second aspect, the cellulose raw material is mixed with a compound having a phosphite group and/or a salt thereof and urea and/or a urea derivative to obtain a phosphite group or a phosphite group. And a step of obtaining a cellulose raw material having a substituent. Then, in the step of obtaining a phosphorous acid group or a substituent cellulose raw material derived from a phosphorous acid group, a compound and/or a salt thereof having a phosphorous acid group and urea and/or a urea derivative are added to the cellulose raw material. The decomposition rate of urea and/or urea derivative in one cycle process is 95% or less including one cycle process of mixing and heating.

In the following, the step of obtaining a cellulose raw material having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, or a step of obtaining a cellulose raw material having a phosphorous acid group or a substituent derived from a phosphorous acid group Also referred to as an acid group introduction step.

In the method for producing fibrous cellulose of the present invention, as in the second aspect, a compound having a phosphite group and/or a salt thereof and urea and/or a urea derivative are mixed with a cellulose raw material. It is preferable. Here, the carbonyl group and amino group of urea form a hydrogen bond with the phosphite group of the compound having a phosphite group, and suppress the ionization of hydrogen ions. On the other hand, since urea is decomposed by heat or the like, when decomposed, it is released outside the reaction system as carbon dioxide gas or ammonia gas. In the method for producing fibrous cellulose of the present invention, by suppressing the decomposition rate of urea and/or urea derivative to 95% or less, the hydrogen bond between urea and the phosphite group can be retained, whereby Ionization of hydrogen ions from the phosphate group can be suppressed. Since the pKa of phosphorous acid is smaller than the pKa of phosphoric acid, hydrogen ions of the phosphite group are easily ionized, which lowers the acidity of the system and deteriorates the fibrous cellulose or urea. It is thought that the decomposition of the is easily promoted. However, in the present invention, by setting the decomposition rate of urea and/or urea derivative to 95% or less, ionization of hydrogen ions can be suppressed even in fibrous cellulose having a phosphite group, and as a result, fibrous cellulose It is possible to suppress deterioration and the like.

Since the fibrous cellulose of the present invention is obtained through such a manufacturing process, the fibrous cellulose is micronized, and when the resulting fine fibrous cellulose is dispersed in a dispersion medium to prepare a dispersion liquid, A highly transparent dispersion is obtained. When a molded product such as a sheet is molded using such a dispersion medium, a highly transparent sheet can be obtained. Further, the fibrous cellulose and the fine fibrous cellulose of the present invention are suppressed in yellowing, and when a sheet is formed from a dispersion liquid containing the fine fibrous cellulose, a sheet having a low YI value can be obtained.

<Cellulose raw material>
The fine fibrous cellulose is produced from a fiber raw material (cellulose raw material) containing cellulose. The fiber raw material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Pulps include, for example, wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, and examples thereof include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP). ) And chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP) etc. Examples include mechanical pulp. The non-wood pulp is not particularly limited, but examples thereof include cotton-based pulp such as cotton linter and cotton lint, and non-wood-based pulp such as hemp, straw and bagasse. The deinked pulp is not particularly limited, and examples thereof include deinked pulp made from waste paper. The pulp of the present embodiment may be used alone or as a mixture of two or more kinds. Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of easy availability. Further, among wood pulp, a viewpoint of a high yield of fine fibrous cellulose at the time of defibration treatment with a large cellulose ratio and a long fiber fine fibrous cellulose with a small decomposition of cellulose in the pulp and a large axial ratio can be obtained. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. The viscosity tends to increase when fine fibrous cellulose of long fibers having a large axial ratio is used.

As the fiber raw material containing cellulose, for example, cellulose contained in ascidians or bacterial cellulose produced by acetic acid bacteria can be used. Further, instead of the fiber raw material containing cellulose, a fiber formed by a linear nitrogen-containing polysaccharide polymer such as chitin or chitosan may be used.

<Phosphorus oxo acid group introduction step>
In the phosphorus oxo acid group introducing step in the first aspect, a cellulose raw material having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group is prepared by mixing phosphorus oxo acid and/or a salt thereof with urea and/or a urea derivative. It is a process of obtaining. Here, in the step of obtaining a cellulose raw material having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, the cellulose raw material is mixed with phosphorus oxo acid and/or a salt thereof and urea and/or a urea derivative, and heated. It includes a plurality of one-cycle processes. In the phosphorous acid group-introducing step in the second aspect, a compound having a phosphorous acid group and/or a salt thereof and urea and/or a urea derivative are mixed into the cellulose raw material to have a phosphorous acid group. This is a step of obtaining a cellulose raw material. Here, in the step of obtaining a phosphorous acid group or a substituent cellulose raw material derived from a phosphorous acid group, the cellulose raw material is mixed with phosphorous acid and/or a salt thereof and urea and/or a urea derivative, A plurality of one cycle steps of heating are included. In the phosphorus oxo acid group introduction step of the first aspect, the phosphorus oxo acid group can be introduced by reacting the hydroxyl group of the cellulose-containing fiber raw material with the phosphorus oxo acid and/or its salt. In the phosphorous oxo group introduction step of the second aspect, the phosphite group is introduced by reacting the hydroxyl group of the cellulose-containing fiber raw material with the compound having the phosphite group and/or its salt. You can In the present specification, a compound containing a phosphorous acid and/or a salt thereof, or a compound having a phosphorous acid group and/or a salt thereof may be referred to as a compound A, and urea and/or a urea derivative may be referred to as a compound B. Sometimes called.

As an example of a method of allowing the compound A to act on the fiber raw material in the coexistence with the compound B, a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state or a slurry state can be mentioned. Among these, it is preferable to use a fiber raw material in a dry state or a wet state, and particularly preferable to use a fiber raw material in a dry state, since the reaction is highly uniform. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Compound A and compound B may be added to the fiber raw material in the form of powder or solution dissolved in a solvent, or heated to a melting point or higher and melted. Among these, since the reaction is highly uniform, it is preferable to add them in the form of a solution dissolved in a solvent, particularly in the state of an aqueous solution. Further, the compound A and the compound B may be added to the fiber raw material at the same time, may be added separately, or may be added as a mixture. The method of adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be dipped in the solution to absorb the liquid, and then taken out. The solution may be added dropwise. Further, the required amounts of compound A and compound B may be added to the fiber raw material, or excess amounts of compound A and compound B may be respectively added to the fiber raw material, and then excess compound A and compound B may be squeezed or filtered. May be removed.

Examples of the compound A used in this embodiment include compounds having a phosphorus atom and capable of forming an ester bond with cellulose. The compound A contains at least a compound having a phosphorous acid group and/or a salt thereof. It is preferable. Examples of the compound having a phosphorous acid group include phosphorous acid, and examples of the phosphorous acid include 99% phosphorous acid (phosphonic acid). Examples of the salt of phosphorous acid include lithium salt, sodium salt, potassium salt, and ammonium salt of phosphorous acid, which can have various degrees of neutralization. Among these, from the viewpoint of high efficiency of introduction of phosphorus oxo acid group, easier improvement of defibration efficiency in the defibration step described later, low cost, and easy industrial application, phosphorous acid, phosphorus phosphite The sodium salt of an acid, the potassium salt of phosphorous acid, or the ammonium salt of phosphorous acid is preferable, and phosphorous acid is more preferable. In addition to the compound having a phosphorous acid group and/or a salt thereof, the compound A is a compound having a phosphoric acid group and/or a salt thereof, dehydrated condensed phosphoric acid and/or a salt thereof, and phosphoric anhydride (pentoxide). Diphosphorus) and the like. In this case, phosphoric acid having various purities can be used, and for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. The dehydrated condensed phosphoric acid is one in which two or more molecules of phosphoric acid are condensed by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid.

The addition amount of the compound A to the fiber raw material is not particularly limited, but when the addition amount of the compound A is converted into the phosphorus atomic weight, the addition amount of the phosphorus atom to the fiber raw material (absolute dry mass) is 0.5% by mass or more. It is preferably 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, still more preferably 2% by mass or more and 30% by mass or less. By setting the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by controlling the amount of phosphorus atoms added to the fiber raw material to be not more than the above upper limit, the effect of improving the yield and the cost can be balanced.

The compound B used in this embodiment is urea and/or a urea derivative as described above. Examples of the compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like. From the viewpoint of improving the uniformity of the reaction, the compound B is preferably used as an aqueous solution. From the viewpoint of further improving the homogeneity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

The amount of the compound B added to the fiber raw material (absolute dry mass) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, More preferably, it is 100% by mass or more and 350% by mass or less.

When the molar mass (mmol) of the phosphorus atom contained in the compound A is P and the molar mass (mmol) of urea and/or the urea derivative contained in the compound B is N, the value of N/P is 3 It is preferably at least 0.5, more preferably at least 4.0, even more preferably at least 4.5, and particularly preferably at least 5.0. The N/P value is preferably 50 or less. By setting the value of N/P within the above range, it becomes easy to control the decomposition rate of urea and/or urea derivative in the phosphorus oxo acid group introduction step to 95% or less.

In the reaction between the fiber raw material containing cellulose and the compound A, in addition to the compound B, for example, amides or amines may be included in the reaction system. Examples of the amides include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Of these, triethylamine is known to work particularly as a good reaction catalyst.

In the phosphorus oxo acid group introduction step, it is preferable to heat the fiber raw material after adding or mixing the compound A or the like to the fiber raw material (heat treatment step). As the heat treatment temperature in the heat treatment step, it is preferable to select a temperature at which a phosphorus oxo acid group such as a phosphorous acid group can be efficiently introduced while suppressing thermal decomposition or hydrolysis reaction of the fiber. The heat treatment temperature may vary depending on the heating time and the selection of the heat source, but it is preferably 50°C or higher, more preferably 100°C or higher, and further preferably 130°C or higher. The heat treatment temperature is preferably 250° C. or lower, more preferably 175° C. or lower. Further, for the heat treatment, equipment having various heat mediums can be used, for example, a stirring dryer, a rotary dryer, a disc dryer, a roll heater, a plate heater, a fluidized bed dryer, and an air flow. A drying device, a reduced pressure drying device, an infrared heating device, a far infrared heating device, a microwave heating device, and a high frequency drying device can be used.

In the heat treatment according to the present embodiment, for example, a method of adding compound A to a thin sheet-shaped fiber raw material by a method such as impregnation and then heating, or heating while kneading or stirring the fiber raw material and compound A with a kneader or the like. Can be adopted. This makes it possible to suppress uneven concentration of the compound A in the fiber raw material and more uniformly introduce a phosphorous acid group such as a phosphorous acid group into the surface of the cellulose fiber contained in the fiber raw material. This is because when water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A is attracted to the water molecules due to the surface tension and similarly moves to the surface of the fiber raw material (that is, uneven concentration of compound A It is thought to be due to the fact that it can be suppressed.

In addition, the heating device used for the heat treatment always keeps, for example, the water retained by the slurry and the water generated by the dehydration condensation (phosphoric acid esterification) reaction between the compound A and the hydroxyl groups contained in the cellulose or the like in the fiber raw material. It is preferable that the device can be discharged to the outside of the device system. An example of such a heating device is a blower type oven. By constantly discharging the water in the device system, in addition to suppressing the hydrolysis reaction of the phosphoric acid ester bond, which is the reverse reaction of phosphoric acid esterification, it is also possible to suppress the acid hydrolysis of sugar chains in the fiber. it can. Therefore, it becomes possible to obtain fine fibrous cellulose having a high axial ratio.

The heat treatment time is preferably 10 seconds or more, more preferably 100 seconds or more, further preferably 200 seconds or more, and more preferably 300 seconds or more from the state in which the fiber raw material contains water. Is particularly preferable. The heat treatment time is preferably 10,000 seconds or less, more preferably 5000 seconds or less, further preferably 3000 seconds or less, and particularly preferably 2000 seconds or less. In addition, the time of the said heat processing is a total time of the heating time in all cycle processes. In the present embodiment, the introduction amount (A1) of the phosphorus oxo acid group can be set within the preferable range by setting the heating temperature and the heating time within appropriate ranges.

The phosphorus oxo acid group introduction step in the first aspect includes a plurality of one cycle steps in which a phosphorus oxo acid and/or a salt thereof and urea and/or a urea derivative are mixed with a cellulose raw material and heated. Further, the phosphorus oxo acid group introducing step in the second aspect includes a plurality of one cycle steps of mixing phosphorous acid and/or a salt thereof, urea and/or urea derivative into a cellulose raw material and heating the mixture. Specifically, one cycle process in which phosphorous acid and/or a salt thereof or phosphorous acid and/or a salt thereof and urea and/or a urea derivative are mixed and heated may be provided in two steps. Three steps may be provided, or four or more steps may be provided. That is, in the phosphorus oxo acid group introduction step, the above-mentioned 1 cycle step may be repeated twice, repeated three times, or repeated four times or more. The number of repetitions of the one cycle process is preferably 10 times or less.

The heat treatment time for each cycle step is preferably 1 second or more, more preferably 10 seconds or more, further preferably 50 seconds or more, from the state that the fiber raw material contains water, and 100 is more preferable. Particularly preferably, it is not less than 2 seconds. Further, the heat treatment time is preferably 5000 seconds or less, more preferably 3000 seconds or less, further preferably 2000 seconds or less, further preferably 1000 seconds or less, and less than 900 seconds. Is particularly preferable. In the present invention, for example, by setting the heat treatment time for each cycle step within the above range and repeating such a cycle a plurality of times, the decomposition rate of urea and/or urea derivative can be adjusted to an appropriate range. You can control. Further, by adjusting the addition amount of phosphorus oxo acid and/or its salt, or phosphorous acid and/or its salt, and urea and/or urea derivative, and adjusting the heating temperature, urea and/or Alternatively, the decomposition rate of the urea derivative may be controlled within an appropriate range.

The decomposition rate of urea and/or urea derivative in the one-cycle step may be 95% or less, preferably 94% or less, and more preferably 93% or less. The lower limit of the decomposition rate of urea and/or the urea derivative in the one cycle process is not particularly limited, but is preferably 10% or more. In the method for producing fibrous cellulose of the present invention. Although the above-described one-cycle process is provided a plurality of times, it is preferable that the decomposition rate of urea and/or the urea derivative in all the one-cycle processes be equal to or less than the upper limit value.

Here, the urea decomposition rate is the mass reduction of urea added to the cellulosic raw material divided by the mass decrease other than evaporation of water in the phosphorus oxo acid introduction step (particularly heating), that is, the mass fraction. It is a value expressed as a rate. Urea is decomposed by heat or the like and released to the outside of the reaction system as carbon dioxide gas or ammonia gas. Therefore, the urea decomposition rate is calculated by the following method.
First, the absolute dry mass of the cellulose raw material (pulp) used in the test is measured. Next, a predetermined amount of chemical liquid is added to the cellulose raw material (pulp), and the mass is measured (m ₀ ). From the chemical composition and the initial moisture content of the pulp, the amount of water added (water content of the system) (m _w ) and the amount of urea added (m _u ) are calculated. Then, the impregnated cellulose raw material (pulp) is heat-treated under the heat-treatment conditions as described above, and the mass is measured (m ₁ ). The urea decomposition rate [%] is calculated from the following (Formula 1) using the measured and calculated mass.
Urea decomposition rate [%]=(m ₀ −m _w −m ₁ )/mu _u ×100 (Equation 1)
m ₀ : mass of chemical-impregnated pulp before heating m _w : amount of added water (water content of system)
m ₁ : mass of pulp after heating m _u : amount of urea added When the phosphorus oxo acid introduction step is repeated a plurality of times, the above cellulose raw material (pulp) is replaced with a phosphorus oxo oxidized pulp to be subjected to a plurality of reactions, and the same. Calculate.

In the method for producing fibrous cellulose of the present invention, fibrous cellulose is prepared by controlling the decomposition rate of urea and/or urea derivative in the phosphorus oxo acid group introduction step so as to satisfy the above conditions, and then performing defibration treatment. When dispersed in a dispersion medium to obtain a dispersion liquid, a highly transparent dispersion liquid is obtained. When a molded product such as a sheet is molded using such a dispersion medium, a highly transparent sheet can be obtained. Furthermore, the yellowing of the fibrous cellulose of the present invention is suppressed, and when a sheet is formed from a dispersion liquid containing fibrous cellulose, a sheet having a low YI value can be obtained.

The YI value of the phosphorus oxo acid group-introduced fiber (phosphorous oxide pulp) obtained in the above-described phosphorus oxo acid group introduction step is preferably 42.0 or less, and more preferably 36.0 or less. It is more preferably 30.0 or less, and particularly preferably 24.0 or less. The YI value of the fiber having a phosphorous acid group introduced is a value measured according to JIS K7373. As the measuring device, for example, Color Cute i manufactured by Suga Test Instruments Co., Ltd. can be used.

<Washing process>
In the method for producing fine fibrous cellulose according to the present embodiment, a washing step can be performed on the phosphorus oxo acid group-introduced fiber, if necessary. The washing step is performed, for example, by washing the phosphorus oxo acid group-introduced fiber with water or an organic solvent. The cleaning step may be performed after each step described below, and the number of times of cleaning performed in each cleaning step is not particularly limited.

<Alkali treatment process>
In the case of producing fine fibrous cellulose, the fiber raw material may be subjected to an alkali treatment between the phosphorus oxo acid group introduction step and the defibration treatment step described later. The method of alkali treatment is not particularly limited, and examples thereof include a method of immersing the phosphorous acid group-introduced fiber in an alkali solution.

The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In this embodiment, for example, sodium hydroxide or potassium hydroxide is preferably used as the alkali compound because of its high versatility. Further, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.

The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5° C. or higher and 80° C. or lower, and more preferably 10° C. or higher and 60° C. or lower. The time for immersing the phosphorus oxo acid group-introduced fiber in the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but for example, it is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less based on the absolutely dry mass of the phosphorus oxo acid group-introduced fiber. Is more preferable.

In order to reduce the amount of the alkaline solution used in the alkali treatment step, the phosphorus oxo acid group-introduced fiber may be washed with water or an organic solvent after the phosphorus oxo acid group introduction step and before the alkali treatment step. After the alkali treatment step and before the defibration treatment step, it is preferable to wash the alkali-treated phosphorus oxo acid group-introduced fiber with water or an organic solvent from the viewpoint of improving handleability.

<Acid treatment step>
In the case of producing fine fibrous cellulose, an acid treatment may be performed on the phosphorus oxo acid group-introduced fiber between the step of introducing the phosphorus oxo acid group and the defibration treatment step described later. For example, the phosphorus oxo acid group introduction step, the acid treatment, the alkali treatment and the defibration treatment may be performed in this order.

The method of acid treatment is not particularly limited, and examples thereof include a method of immersing the phosphoroxo acid group-introduced fiber in an acid-containing acidic liquid. The concentration of the acidic liquid used is not particularly limited, but is, for example, preferably 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic liquid used is not particularly limited, but is, for example, preferably 0 or more and 4 or less, and more preferably 1 or more and 3 or less. As the acid contained in the acidic liquid, for example, an inorganic acid, a sulfonic acid, a carboxylic acid or the like can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, boric acid and the like. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid and the like. Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid and the like. Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5°C or higher and 100°C or lower, more preferably 20°C or higher and 90°C or lower. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more and 120 minutes or less, more preferably 10 minutes or more and 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less, with respect to the absolutely dry mass of the phosphorus oxo acid group-introduced fiber. Is more preferable.

<Fibration process>
When producing fibrous cellulose having a fiber width of 1000 nm or less, the method for producing fibrous cellulose may include a defibration treatment step. In the defibration treatment step, a cellulose raw material having a substituent derived from a phosphorus oxo acid group or a phosphorus oxo acid group, or a cellulose raw material having a substituent derived from a phosphorous acid group or a phosphorous acid group is subjected to a refining treatment, This is a step of obtaining fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorous acid group such as a phosphorous acid group. In the defibration processing step, for example, a defibration processing device can be used. The defibration treatment device is not particularly limited, but includes, for example, a high-speed defibration device, a grinder (stone mill type crusher), a high pressure homogenizer or an ultrahigh pressure homogenizer, a high pressure collision type crusher, a ball mill, a bead mill, a disc type refiner, a conical refiner, a twin screw A kneader, a vibration mill, a homomixer under high speed rotation, an ultrasonic disperser, a beater, or the like can be used. Among the above defibration treatment devices, it is more preferable to use a high-speed defibration machine, a high-pressure homogenizer, and an ultrahigh-pressure homogenizer that are less affected by the grinding media and less likely to cause contamination.

In the defibration treatment step, it is preferable to dilute the fiber into which a phosphorous acid group such as a phosphite group has been introduced with a dispersion medium to form a slurry. As the dispersion medium, water and one or more selected from organic solvents such as polar organic solvents can be used. The polar organic solvent is not particularly limited, but alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents and the like are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of the ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, and propylene glycol monomethyl ether. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

The solid content concentration of the fine fibrous cellulose during the defibration treatment can be set appropriately. Further, the slurry obtained by dispersing the phosphite group-introduced fiber in a dispersion medium may contain solid components other than the phosphorus oxo acid group-introduced fiber such as urea having hydrogen bonding property.

(Fibrous cellulose-containing composition)
The present invention may relate to a fibrous cellulose-containing composition containing the above-mentioned fibrous cellulose. In the present specification, the fibrous cellulose-containing composition may be a composition containing a solvent in addition to the fibrous cellulose described above. The type of solvent is not particularly limited, and examples thereof include water, an organic solvent, and a mixture of water and an organic solvent. Examples of the organic solvent include alcohols, polyhydric alcohols, ketones, ethers, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and the like. Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol and glycerin. Examples of the ketones include acetone and methyl ethyl ketone. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, and ethylene glycol mono t-butyl ether.

In the fibrous cellulose-containing composition, when the solvent is the main component, the fibrous cellulose-containing composition may be a liquid composition. Further, in the fibrous cellulose-containing composition, when the content of the solvent is small, the fibrous cellulose-containing composition may be a solid composition. The solid composition also includes a gel composition and a powdery composition.

When the fibrous cellulose-containing composition is a liquid composition, the solid content concentration in the liquid composition is preferably 0.1% by mass or more and 1% by mass or more based on the total mass of the liquid composition. Is more preferable, and 5% by mass or more is further preferable. The solid content concentration in the liquid composition is preferably 90% by mass or less, and more preferably 50% by mass or less, based on the total mass of the liquid composition. Further, when the fibrous cellulose-containing composition is a solid composition, the solid content concentration in the solid composition is preferably 50% by mass or more based on the total mass of the solid composition, 80 It is more preferably at least mass% and even more preferably at least 90 mass %. Further, the solid content concentration in the solid composition is preferably 99.9% by mass or less, and more preferably 95% by mass or less, based on the total mass of the solid composition.

When the fibrous cellulose-containing composition is a liquid composition containing water as a solvent, the total light transmittance of the liquid composition when the content of the fibrous cellulose contained in the liquid composition is 0.2% by mass. Is preferably 80% or more, more preferably 90% or more, further preferably 95% or more, and particularly preferably 98% or more. Here, the total light transmittance of the liquid composition is a value measured according to JIS K7361. The total light transmittance of the liquid composition is measured using a haze meter. At this time, a glass cell for liquid having an optical path length of 1 cm is used. The zero point measurement is performed with ion-exchanged water contained in the glass cell. Before the measurement, the liquid composition is allowed to stand for 24 hours in an environment of 23° C. and a relative humidity of 50% so that the liquid temperature of the liquid composition is 23° C. In addition, that the total light transmittance of the liquid composition is within the above range also means that the phosphorus oxo acid group of the fibrous cellulose is not excessively condensed.

When the fibrous cellulose-containing composition is a liquid composition containing water as a solvent, the haze of the liquid composition is preferably 25% or less, more preferably 20% or less, and 15% or less. Is more preferable, 10% or less is more preferable, and 5% or less is particularly preferable. The haze of the liquid composition may be 0%. The haze value is a value measured according to JIS K 7136 after diluting the fibrous cellulose-containing composition with ion-exchanged water to 0.2% by mass. A haze meter is used for the measurement of haze, and the dispersion liquid is filled in a glass cell for liquid having an optical path length of 1 cm. The zero point measurement is performed with ion-exchanged water contained in the glass cell.

The B-type viscosity when the content of the fibrous cellulose contained in the liquid composition is 0.4% by mass is preferably 5000 mPa·s or more, more preferably 8000 mPa·s or more, and 10000 mPas. -It is more preferable that it is s or more. The upper limit of the viscosity of the liquid composition is not particularly limited, but it is preferably 100000 mPa·s. The above-mentioned viscosity is obtained by diluting the liquid composition so that the solid content concentration becomes 0.4% by mass, and then stirring the same at 1500 rpm for 5 minutes with a disperser to sufficiently homogenize the slurry at 23° C. and relative humidity. It is a value measured using a B-type viscometer after standing still for 24 hours in a 50% environment. The measurement condition is set to 23° C., and the viscosity when rotated at 3 rpm for 3 minutes is measured. As the measuring device, an analog viscometer T-LVT manufactured by BLOOKFIELD can be used.

When the fibrous cellulose-containing composition is a liquid composition containing a solvent, the fibrous cellulose-containing composition may be a slurry obtained in the above defibration treatment step. In addition, after concentrating or drying the slurry obtained in the defibration treatment step to form a gel-like or solid fibrous cellulose-containing material, the fibrous cellulose-containing material is redispersed in a solvent to form fibers. A cellulose-containing composition (fibrous cellulose dispersion) may be used.

<Arbitrary ingredients>
The fibrous cellulose-containing composition may further contain optional components. Examples of the optional component include a defoaming agent, a lubricant, an ultraviolet absorber, a dye, a pigment, a stabilizer, a surfactant, and a preservative. Further, the fibrous cellulose-containing composition may contain, as an optional component, a hydrophilic polymer, a hydrophilic low molecule, an organic ion or the like.

The hydrophilic polymer is preferably a hydrophilic oxygen-containing organic compound (excluding the above-mentioned cellulose fiber). Examples of the oxygen-containing organic compound include polyethylene glycol, polyethylene oxide, casein, dextrin, starch, and modified Starch, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylates, alkyl acrylate copolymers, urethane copolymers, cellulose derivatives (hydroxyethyl cellulose, carboxy) Ethyl cellulose, carboxymethyl cellulose, etc.) and the like.

The hydrophilic low-molecular weight compound is preferably a hydrophilic oxygen-containing organic compound, more preferably a polyhydric alcohol. Examples of the polyhydric alcohol include glycerin, sorbitol, ethylene glycol and the like.

Examples of organic ions include tetraalkylammonium ions and tetraalkylphosphonium ions. Examples of the tetraalkylammonium ion include tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, tetraheptylammonium ion, tributylmethylammonium ion, and lauryltrimethyl. Examples thereof include ammonium ion, cetyl trimethyl ammonium ion, stearyl trimethyl ammonium ion, octyl dimethyl ethyl ammonium ion, lauryl dimethyl ethyl ammonium ion, didecyl dimethyl ammonium ion, lauryl dimethyl benzyl ammonium ion, and tributyl benzyl ammonium ion. Examples of the tetraalkylphosphonium ion include tetramethylphosphonium ion, tetraethylphosphonium ion, tetrapropylphosphonium ion, tetrabutylphosphonium ion, and lauryltrimethylphosphonium ion. Moreover, as tetrapropyl onium ion and tetrabutyl onium ion, tetra n-propyl onium ion, tetra n-butyl onium ion, etc. can be mentioned, respectively.

(Molded body)
The present invention may relate to the above-mentioned fibrous cellulose or a molded body formed from the above-mentioned fibrous cellulose-containing composition. In the present specification, the molded body is a solid body that is molded into a desired shape. Examples of the molded body include sheets, beads, filaments and the like. Above all, the molded body is preferably a sheet, beads or filament. When the molded product is in the form of beads, the particle diameter of the beads is preferably 0.1 mm or more and 10 mm or less. When the molded product is in the form of a filament, the width of the filament is preferably 0.1 mm or more and 10 mm or less, and the length of the filament is preferably 1 mm or more and 10000 mm or less.

(Sheet)
Above all, the molded body is preferably in the form of a sheet, and the present invention may be related to a sheet formed from the above-mentioned fibrous cellulose-containing composition. Here, when a sheet is formed under the following condition (a), the YI value of the sheet may be 6.0 or less, preferably 4.5 or less, and more preferably 3.0 or less. , 1.5 or less is more preferable. The lower limit of the YI value of the sheet is not particularly limited and may be 0.0. The YI value of the sheet is a value measured according to JIS K7373. As the measuring device, for example, Color Cute i manufactured by Suga Test Instruments Co., Ltd. can be used.
Condition (a):
A fibrous cellulose dispersion having a solid content concentration of 0.5% by mass was prepared, and 20 parts by mass of an aqueous polyethylene oxide solution having a concentration of 0.5% by mass was added to 100 parts by mass of the fibrous cellulose dispersion, followed by coating. A coating solution is applied onto a substrate to form a sheet having a basis weight of 50 g/m ² .

When measuring the YI value and total light transmittance of the sheet, each measurement is performed on the sheet having a basis weight of 50 g/m ² . However, it is also possible that the basis weight of the obtained sheet is not 50 g/m ² . In such a case, a step of redispersing the sheet in water to prepare a sheet having a basis weight of 50 g/m ² can be provided before the measurement.

The thickness of the sheet of the present invention is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. The upper limit of the thickness of the sheet is not particularly limited, but may be, for example, 1000 μm. The thickness of the sheet can be measured by, for example, a stylus thickness meter (Millitron 1202D manufactured by Marl).

The basis weight of the sheet is not particularly limited, but is preferably 10 g/m ² or more, more preferably 20 g/m ² or more, and further preferably 30 g/m ² or more. The basis weight of the sheet is not particularly limited, but is preferably 200 g/m ² or less, and more preferably 180 g/m ² or less. Here, the basis weight of the sheet can be calculated in accordance with JIS P 8124, for example.

The density of the sheet is not particularly limited, but is preferably 0.1 g/cm ³ or more, more preferably 0.5 g/cm ³ or more, and further preferably 1.0 g/cm ³ or more. preferable. The density of the sheet is not particularly limited, but is preferably 5.0 g/cm ³ or less, and more preferably 3.0 g/cm ³ or less. Here, the density of the sheet can be calculated by measuring the thickness and mass of the sheet after conditioning the 50 mm square sheet at 23° C. and 50% relative humidity for 24 hours.

The content of fibrous cellulose in the sheet is, for example, preferably 0.5% by mass or more, more preferably 1% by mass or more, and more preferably 5% by mass or more, based on the total mass of the sheet. Is more preferable and 10% by mass or more is particularly preferable. On the other hand, the upper limit of the content of fibrous cellulose in the sheet is not particularly limited, and may be 100% by mass or 95% by mass with respect to the total mass of the sheet.

The sheet may include optional components that may be included in the fibrous cellulose-containing composition. Further, the sheet may contain water or an organic solvent.

(Sheet manufacturing method)
The method for producing a fine fibrous cellulose-containing sheet is, as described later, a coating step of coating a fibrous cellulose-containing composition (hereinafter also referred to as a fibrous cellulose dispersion or slurry) on a substrate, or the slurry. It is preferable to include a paper making step of making paper.

<Coating process>
In the coating step, a sheet can be obtained by, for example, coating a fibrous cellulose-containing composition (slurry) on a base material, and drying the formed sheet to peel off the formed sheet from the base material. Further, the sheet can be continuously produced by using the coating device and the long base material.

The material of the base material used in the coating step is not particularly limited, but the one having higher wettability to the fibrous cellulose-containing composition (slurry) may be able to suppress the shrinkage of the sheet during drying, It is preferable to select a sheet from which the sheet formed after drying can be easily peeled off. Of these, a resin film or plate or a metal film or plate is preferable, but not particularly limited. For example, resin films and plates of polypropylene, acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polycarbonate, polyvinylidene chloride, etc., metal films and plates of aluminum, zinc, copper, iron plates, and those whose surfaces are oxidized. A stainless film or plate, a brass film or plate, or the like can be used.

In the coating process, when the viscosity of the slurry is low and spreads on the base material, a damming frame should be fixed on the base material in order to obtain a sheet with a predetermined thickness and basis weight. May be. The damming frame is not particularly limited, but it is preferable to select, for example, a frame in which the edge of the sheet attached after drying can be easily peeled off. From this point of view, a molded resin plate or metal plate is more preferable. In this embodiment, for example, a polypropylene plate, an acrylic plate, a polyethylene terephthalate plate, a vinyl chloride plate, a polystyrene plate, a polycarbonate plate, a polyvinylidene chloride plate, or another resin plate, or an aluminum plate, a zinc plate, a copper plate, an iron plate, or another metal plate. It is also possible to use those whose surfaces are oxidized and which are molded stainless steel plates, brass plates and the like. The coating machine for coating the slurry on the base material is not particularly limited, but a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater or the like can be used. A die coater, a curtain coater, and a spray coater are particularly preferable because the thickness of the sheet can be made more uniform.

The slurry temperature and the ambient temperature when applying the slurry to the substrate are not particularly limited, but are preferably 5° C. or higher and 80° C. or lower, more preferably 10° C. or higher and 60° C. or lower, and 15° C. The temperature is more preferably 50° C. or lower and more preferably 20° C. or higher and 40° C. or lower. When the coating temperature is at least the above lower limit, the slurry can be coated more easily. If the coating temperature is at most the above upper limit, volatilization of the dispersion medium during coating can be suppressed.

In the coating step, the slurry is used so that the finished basis weight of the sheet is preferably 10 g/m ² or more and 200 g/m ² or less, more preferably 20 g/m ² or more and 180 g/m ² or less. It is preferable to coat the material. By coating so that the basis weight is within the above range, a sheet having excellent strength can be obtained.

As described above, the coating step includes a step of drying the slurry coated on the base material. The step of drying the slurry is not particularly limited, but is performed by, for example, a non-contact drying method, a method of drying while restraining the sheet, or a combination thereof.

The non-contact drying method is not particularly limited, but for example, a method of heating and drying with hot air, infrared rays, far infrared rays or near infrared rays (heating drying method) or a method of drying in vacuum (vacuum drying method) is applied. can do. The heat drying method and the vacuum drying method may be combined, but the heat drying method is usually applied. Drying with infrared rays, far infrared rays, or near infrared rays is not particularly limited, but can be performed using, for example, an infrared device, a far infrared device, or a near infrared device.

The heating temperature in the heating and drying method is not particularly limited, but is preferably 20° C. or higher and 150° C. or lower, and more preferably 25° C. or higher and 105° C. or lower. When the heating temperature is at least the above lower limit, the dispersion medium can be volatilized quickly. When the heating temperature is at most the above upper limit, it is possible to suppress the cost required for heating and suppress the discoloration of fibrous cellulose due to heat.

<Papermaking process>
The papermaking process is performed by making the slurry into paper using a paper machine. The paper machine used in the paper making process is not particularly limited, and examples thereof include a fourdrinier type, cylinder type, inclined type and the like continuous paper machine, and a multi-layered paper machine combining them. In the paper making process, a known paper making method such as hand making may be adopted.

The papermaking step is performed by filtering the slurry with a wire and dehydrating it to obtain a wet paper sheet, and then pressing and drying this sheet. The filter cloth used for filtering and dehydrating the slurry is not particularly limited, but it is more preferable that, for example, fibrous cellulose does not pass through and the filtration rate does not become too slow. The filter cloth is not particularly limited, but a sheet, a woven fabric, and a porous membrane made of an organic polymer are preferable. The organic polymer is not particularly limited, but non-cellulosic organic polymers such as polyethylene terephthalate, polyethylene, polypropylene and polytetrafluoroethylene (PTFE) are preferable. In the present embodiment, for example, a polytetrafluoroethylene porous film having a pore diameter of 0.1 μm or more and 20 μm or less, a polyethylene terephthalate or polyethylene woven fabric having a pore diameter of 0.1 μm or more and 20 μm or less, and the like can be mentioned.

In the sheet-forming step, a method for producing a sheet from the slurry includes, for example, discharging a slurry containing fibrous cellulose onto the upper surface of an endless belt, and squeezing a dispersion medium from the discharged slurry to form a web. , A drying section for drying the web to produce a sheet. An endless belt is arranged from the water squeezing section to the drying section, and the web produced in the water squeezing section is conveyed to the drying section while being placed on the endless belt.

The dehydration method used in the papermaking step is not particularly limited, and examples thereof include a dehydration method commonly used in paper production. Among these, a method of dehydrating with a Fourdrinier, a cylinder, an inclined wire or the like, and then further dehydrating with a roll press is preferable. The drying method used in the papermaking step is not particularly limited, and examples thereof include the method used in paper production. Among these, a drying method using a cylinder dryer, a Yankee dryer, hot air drying, a near infrared heater, an infrared heater or the like is more preferable.

(Use)
The fibrous cellulose obtained by the production method of the present invention can be used as a thickener or a particle dispersion stabilizer. Further, the fibrous cellulose obtained by the production method of the present invention can be mixed with a solvent to form a fibrous cellulose dispersion, or a sheet in which fine fibrous cellulose is uniformly dispersed can be formed from the slurry. .. Further, the fibrous cellulose of the present invention can be preferably used for mixing with an organic solvent containing a resin component. By mixing the fine fibrous cellulose of the present invention and an organic solvent containing a resin component, it is possible to form a resin composite in which the fine fibrous cellulose is uniformly dispersed. Similarly, a fine fibrous cellulose redispersion slurry is used to form a film, which can be used as various films.

The fibrous cellulose obtained by the production method of the present invention can be used as a reinforcing agent or an additive in cement, paint, ink, lubricant, etc. A molded product obtained by coating fibrous cellulose on a base material is a reinforcing material, interior material, exterior material, packaging material, electronic material, optical material, acoustic material, process material, member of transportation equipment. It is also suitable for applications such as electronic equipment members and electrochemical element members.

The features of the present invention will be described more specifically below with reference to Examples and Comparative Examples. The materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the following specific examples.

<Production Example 1>
As a raw material pulp, a softwood kraft pulp made by Oji Paper Co., Ltd. (solid content 93 mass %, basis weight 245 g/m ² sheet shape, Canadian standard freeness (CSF) measured according to JIS P 8121 is 700 ml) It was used.

This raw material pulp was subjected to phosphorus oxo oxidation treatment as follows. First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea is added to 100 parts by mass of the raw material pulp (absolute dry mass) to form 33 parts by mass of phosphorous acid (phosphonic acid), 120 parts by mass of urea, and 150 parts of water. The pulp was adjusted to be a mass part to obtain a chemical-impregnated pulp. Then, the obtained chemical liquid-impregnated pulp was heated for 300 seconds with a hot air dryer at 165° C. to introduce phosphorus oxo acid groups into the cellulose in the pulp to obtain phosphorus oxo oxidized pulp 1.

Then, the phosphorous oxidization pulp 1 thus obtained was washed. In the washing treatment, a pulp dispersion obtained by pouring 10 L of ion-exchanged water to 100 g (absolute dry mass) of phosphorus oxo-oxidized pulp 1 is stirred to uniformly disperse the pulp, and then filtration dehydration is repeated. I went by. When the electric conductivity of the filtrate became 100 μS/cm or less, the washing end point was set.

The phosphorus oxo oxidation pulp 1 after washing was further subjected to the above phosphorus oxo oxidation treatment and the above washing treatment twice in this order. (Number of reactions: 3 times).

Then, the washed phosphorous oxidative pulp 1 was subjected to a neutralization treatment as follows. First, the washed phosphorous oxide pulp 1 is diluted with 10 L of ion-exchanged water, and 1N aqueous sodium hydroxide solution is added little by little while stirring to give a phosphorous oxide pulp slurry 1 having a pH of 12 or more and 13 or less. Obtained. Then, the phosphorus oxo-oxidized pulp slurry 1 was dehydrated to obtain a neutralized phosphorus-oxo-oxidized pulp 1. Next, the above-mentioned washing treatment was performed on the phosphorous oxidization pulp 1 after the neutralization treatment.

Infrared absorption spectrum of the thus-obtained phosphoroxoxidized pulp 1 was measured using FT-IR. As a result, the absorption based on P=O of the phosphonic acid group, which is a tautomer of the phosphorous acid group, was observed near 1210 cm ^-1 , and the phosphorous acid group (phosphonic acid group) was added to the pulp. Was confirmed.

Moreover, when the obtained phosphorus oxo-oxidized pulp 1 was tested and analyzed by an X-ray diffractometer, two positions of 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less were determined. Was confirmed to have a typical peak, and it was confirmed to have a cellulose type I crystal.

Ion-exchanged water was added to the obtained phosphorous oxide pulp 1 to prepare a slurry having a solid content concentration of 0.3% by mass. This slurry was treated three times under the condition of 150 MPa using a high-pressure homogenizer (Beryu Mini, manufactured by Bijin Co., Ltd.) to obtain a fine fibrous cellulose dispersion liquid containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that the fine fibrous cellulose maintained the cellulose type I crystal. Moreover, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, fine fibrous cellulose of 3 to 5 nm was observed.

In addition, when the infrared absorption spectrum was similarly measured using FT-IR with respect to the phosphoroxoxidized pulp obtained in all the production examples except Production Example 4, it was found that a phosphorous group was found to be present near 1210 cm ^−1. Absorption based on P=O of the phosphonic acid group, which is a mutant, was observed, and it was confirmed that the phosphorous acid group (phosphonic acid group) was added to the pulp. In addition, when analyzed by an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less. It was confirmed to have crystals.

When the infrared absorption spectrum of the phospho-oxidized pulp obtained in Production Example 4 was similarly measured by using FT-IR, it was found that the phosphonic acid group, which is a tautomer of the phosphite group, was found around 1210 cm ⁻¹ . Absorption based on P=O Absorption based on P=O of the phosphoric acid group was observed near 1230 cm ^-1 , confirming that the phosphorous acid group (phosphonic acid group) and phosphoric acid group were added to the pulp. It was In addition, when analyzed by an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less. It was confirmed to have crystals.

In addition, it was confirmed by X-ray diffraction that the fine fibrous cellulose dispersions obtained in all of the following production examples maintained the cellulose type I crystals. Moreover, when the fiber width was measured using a transmission electron microscope, fine fibrous cellulose having a size of 3 to 5 nm was observed.

<Production Examples 2 and 3>
Fine fibrous cellulose dispersion liquid containing fine fibrous cellulose in the same manner as in Production Example 1 except that the heating time in the hot air dryer in the phosphorus oxo oxidation treatment was 450 seconds (Production Example 2) and 600 seconds (Production Example 3). Got

<Production Example 4>
Instead of 33 parts by mass of phosphorous acid (phosphonic acid), 28 parts by mass of phosphoric acid and 8 parts by mass of phosphorous acid (phosphonic acid) were used, and the heating time in the hot air dryer in the phosphoro-oxo oxidation treatment was 450 seconds. A fine fibrous cellulose dispersion liquid containing fine fibrous cellulose was obtained in the same manner as in Production Example 1 except that the oxidation treatment was repeated once (reaction number: 2 times).

<Production Examples 5 and 6>
Except that the heating time in the hot air dryer in the phosphorus oxo oxidation treatment was 450 seconds (Production Example 5) and 600 seconds (Production Example 6), and the phosphorus oxo oxidation treatment was repeated once (reaction number: 2 times). A fine fibrous cellulose dispersion liquid containing fine fibrous cellulose was obtained in the same manner as in Production Example 1.

<Production Example 7>
Fine fibrous cellulose containing fine fibrous cellulose was produced in the same manner as in Production Example 4 except that the heating time in the hot-air dryer in the phosphorus oxo oxidation treatment was 900 seconds and the phosphorus oxo oxidation treatment was not repeated (reaction number: 1 time). A cellulose dispersion was obtained.

<Production Examples 8 to 10>
The heating time in the hot air dryer in the phosphorus oxo oxidation treatment was set to 900 seconds (Production Example 8), 1350 seconds (Production Example 9), and 1800 seconds (Production Example 10), and the phosphorus oxo oxidation treatment was not repeated (reaction number: 1 Except for the above), a fine fibrous cellulose dispersion liquid containing fine fibrous cellulose was obtained in the same manner as in Production Example 1.

[Measurement and evaluation]
Urea decomposition rate, YI value, and degree of polymerization of the phosphorus oxo-oxidized pulp obtained after the phosphorous-oxidation treatment step or the washing step of Production Examples 1 to 10 were measured according to the evaluation method described below. The haze and the total light transmittance of the fine fibrous cellulose dispersions obtained in Production Examples 1 to 10 were measured according to the evaluation methods described below. Further, a fine fibrous cellulose-containing sheet was prepared by the method described below, and the YI value was measured.

<Calculation of urea decomposition rate>
The urea decomposition rate in each phosphorus oxo oxidation treatment of Production Examples 1 to 10 was calculated by the following method. Here, the urea decomposition rate is a mass fraction obtained by dividing the mass reduction other than evaporation of water in the phosphorus oxo acid introduction step (that is, the decomposition amount of urea) by the mass of urea added to the cellulose raw material. It is a value. This value was measured by the following method.
First, the absolutely dry mass of the cellulose raw material (pulp) used in the test was measured. Next, a predetermined amount of the chemical liquid was added to the cellulose raw material (pulp), and the mass was measured (m ₀ ). From the chemical composition and the initial water content of pulp, the amount of water added (water content of the system) (m _w ) and the amount of urea added (m _u ) were calculated. Then, the impregnated cellulose raw material (pulp) was heat-treated under the heat-treatment conditions as described above, and the mass was measured (m ₁ ). The urea decomposition rate [%] was calculated from the following (Formula 1) using the measured and calculated mass.
Urea decomposition rate [%]=(m ₀ −m _w −m ₁ )/mu _u ×100 (Equation 1)
m ₀ : mass of chemical-impregnated pulp before heating m _w : amount of added water (water content of system)
m ₁ : mass of pulp after heating m _u : amount of urea added When the phosphorus oxo acid introduction step is repeated a plurality of times, the above cellulose raw material (pulp) is replaced with a phosphorus oxo oxidized pulp to be subjected to a plurality of reactions, and the same. Was calculated.

<YI value of phosphorous oxidative pulp>
YI of phosphoroxoxidized pulp was measured by using Color Cute i (manufactured by Suga Test Instruments Co., Ltd.) according to JIS K 7373 for the phosphoroxooxidized pulp immediately after heating (before the washing step) in the phosphoroxooxidation treatment step of Production Examples 1 to 10. The value was measured. When the phosphorus oxo oxidation reaction was performed a plurality of times, the measurement was performed on the phosphorus oxo oxidation pulp immediately after the heating of the last phosphorus oxo oxidation reaction (before the washing step).

<Measurement of Specific Viscosity and Degree of Polymerization of Phosphorus Oxidized Pulp>
The specific viscosity and the degree of polymerization of the fibrous cellulose of the phosphoroxoxidized pulp obtained in the washing steps of Production Examples 1 to 10 were measured according to Tappi T230. That is, after measuring the viscosity (η1) measured by dispersing the fibrous cellulose to be measured in the dispersion medium and the blank viscosity (η0) measured only with the dispersion medium, the specific viscosity (ηsp), the intrinsic viscosity The viscosity ([η]) was measured according to the following formula.
ηsp=(η1/η0)-1
[Η]=ηsp/(c(1+0.28×ηsp))
Here, c in the formula represents the concentration of fibrous cellulose at the time of viscosity measurement.
Furthermore, the degree of polymerization (DP) of fibrous cellulose was calculated from the following formula.
DP=1.75×[η]
Since this degree of polymerization is an average degree of polymerization measured by a viscosity method, it may be referred to as a “viscosity average degree of polymerization”.

<Measurement of first dissociated acid amount and total dissociated acid amount (phosphorus oxo acid group)>
A fibrous cellulose-containing slurry prepared by diluting a fine fibrous cellulose dispersion liquid containing fine fibrous cellulose with ion-exchanged water to a content of 0.2% by mass was treated with an ion-exchange resin. After that, it was measured by performing titration with alkali.
The treatment with the ion-exchange resin was carried out by adding 1/10 by volume of a strongly acidic ion-exchange resin (Amber Jet 1024; Organo Co., Ltd., already conditioned) to the above-mentioned fibrous cellulose-containing slurry and performing a shaking treatment for 1 hour. , And the resin and the slurry were separated by pouring onto a mesh having an opening of 90 μm.
The titration with alkali was performed by adding 0.1N sodium hydroxide aqueous solution to the fibrous cellulose-containing slurry after the treatment with the ion exchange resin and measuring the change in the pH value of the slurry. .. In this neutralization titration, two points at which the increment (the differential value of pH with respect to the amount of alkali added) is maximized are observed in the curve in which the pH measured with respect to the amount of alkali added is plotted. Of these, the maximum point of the increment obtained first after adding alkali is called the first end point, and the maximum point of the increment obtained next is called the second end point (FIG. 1). The amount of alkali required from the start of titration to the first end point becomes equal to the amount of first dissociated acid in the slurry used for titration. Further, the amount of alkali required from the start of titration to the second end point becomes equal to the total amount of dissociated acid in the slurry used for titration. A value obtained by dividing the alkali amount (mmol) required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated was defined as the first dissociated acid amount (mmol/g). A value obtained by dividing the amount of alkali (mmol) required from the start of titration to the second end point by the solid content (g) in the slurry to be titrated was taken as the total dissociated acid amount (mmol/g).

The amounts of the first dissociated acid and the total amount of dissociated acid were also measured for the phosphoroxoxidized pulps obtained in Production Examples 1 to 10. Specifically, 100 parts by mass (absolute dry mass) of the phosphorous oxide pulp obtained in Production Examples 1 to 10 is diluted with ion-exchanged water so that the content becomes 2% by mass, and a 1N hydrochloric acid aqueous solution is stirred. 1000 parts by mass were added little by little. Then, this pulp suspension is stirred for 15 minutes and then dehydrated to obtain a dehydrated sheet, which is then diluted again with ion-exchanged water, and 1000 parts of 1N hydrochloric acid aqueous solution is added to 100 parts by mass of phosphorus oxo-oxidized pulp (absolutely dry mass). Added by mass. By repeating this operation 5 times, the phosphorus oxo acid group contained in the phosphorus oxo oxidized pulp was completely converted to the acid form. Further, the pulp suspension was stirred and uniformly dispersed, and then the operation of obtaining a dehydrated sheet by filtering and dehydrating was repeated to sufficiently wash away excess hydrochloric acid. A high-speed rotary defibrating machine (Clearmix manufactured by M Technique Co., Ltd.) was prepared by diluting the obtained acid-type phosphorus-oxo-oxidized pulp with ion-exchanged water so that the content of the phosphorus-oxo-oxidized pulp was 0.2% by mass. -2.2S), the suspension obtained by mechanical treatment at 21500 rpm for 5 minutes was titrated with an alkali in the same manner as the above-mentioned method.

<Measurement of haze of fine fibrous cellulose dispersion>
The haze of the fine fibrous cellulose dispersion is measured by diluting the fine fibrous cellulose dispersion with ion-exchanged water to 0.2% by mass and then using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.). Was measured in accordance with JIS K 7136 using a glass cell for liquid (MG-40, reverse optical path, manufactured by Fujiwara Seisakusho) having an optical path length of 1 cm. The zero point measurement was performed with ion-exchanged water contained in the glass cell. Further, the dispersion liquid to be measured was allowed to stand for 24 hours in an environment of 23° C. and 50% relative humidity before the measurement. The liquid temperature of the dispersion liquid at the time of measurement was 23°C.

<Measurement of total light transmittance of fine fibrous cellulose dispersion>
The total light transmittance of the fine fibrous cellulose dispersion was measured by diluting the fine fibrous cellulose dispersion with ion-exchanged water to 0.2% by mass, and then using a haze meter (HM-Murakami Color Research Laboratory, HM- 150), using a glass cell for liquid (manufactured by Fujiwara, MG-40, reverse optical path) having an optical path length of 1 cm according to JIS K7361. The zero point measurement was performed with ion-exchanged water contained in the glass cell. Further, the dispersion liquid to be measured was allowed to stand for 24 hours in an environment of 23° C. and 50% relative humidity before the measurement. The liquid temperature of the dispersion liquid at the time of measurement was 23°C.

<Measurement of YI value of sheet containing fine fibrous cellulose dispersion>
The fine fibrous cellulose dispersions obtained in Production Examples 1 to 10 were adjusted in concentration by adding ion-exchanged water so that the solid content concentration became 0.5% by mass. Then, 20 parts by mass of a 0.5% by mass aqueous solution of polyethylene oxide (manufactured by Sumitomo Seika Chemicals Co., Ltd., PEO-18) was added to 100 parts by mass of the fine fibrous cellulose dispersion liquid after concentration adjustment, and the coating liquid was obtained. Obtained. Then, the coating solution is weighed so that the finished basis weight of the obtained sheet (the layer composed of the solid content of the coating solution) is 50 g/m ^2, and the sheet is coated on a commercially available acrylic plate at 50° C. It was dried in a constant temperature dryer. A metal frame for blocking (a metal frame having an inner size of 180 mm×180 mm and a height of 5 cm) was arranged on the acrylic plate so as to have a predetermined basis weight. Then, the dried sheet was peeled from the acrylic plate to obtain a fine fibrous cellulose-containing sheet. Then, according to JIS K 7373, the YI value of the fine fibrous cellulose-containing sheet was measured using Color Cute i (manufactured by Suga Test Instruments Co., Ltd.).

The dispersions containing the fine fibrous cellulose obtained in Production Examples 1 to 6 are highly transparent, and in the sheets formed from the fine fibrous cellulose obtained in Production Examples 1 to 6, yellowing is suppressed. Was there. As described above, it was found that the fine fibrous celluloses obtained in Production Examples 1 to 6 can improve the transparency of the fine fibrous cellulose-containing compositions while suppressing the yellowing of the compositions.

Claims (13)

A fibrous cellulose having a fiber width of 1000 nm or less and having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group,
When the first dissociated acid amount in the fibrous cellulose is A1 and the total dissociated acid amount in the fibrous cellulose is A2, A1 is 1.35 mmol/g or more and the value of A1/A2 is 0.51. Is over,
Fibrous cellulose having a YI value of 6.0 or less when a sheet is formed under the following condition (a);
Condition (a):
A fibrous cellulose dispersion having a solid content concentration of 0.5% by mass was prepared, and 20 parts by mass of an aqueous polyethylene oxide solution having a concentration of 0.5% by mass was added to 100 parts by mass of the fibrous cellulose dispersion, followed by coating. A coating solution is applied onto a substrate to form a sheet having a basis weight of 50 g/m ² . A fibrous cellulose having a fiber width of 1000 nm or less and having a phosphite group or a substituent derived from a phosphite group,
The introduced amount of the phosphite group or the substituent derived from the phosphite group is 1.35 mmol/g or more,
Fibrous cellulose having a YI value of 6.0 or less when the sheet is formed under the following condition (a);
Condition (a):
A fibrous cellulose dispersion having a solid content concentration of 0.5% by mass was prepared, and 20 parts by mass of an aqueous polyethylene oxide solution having a concentration of 0.5% by mass was added to 100 parts by mass of the fibrous cellulose dispersion, followed by coating. A coating solution is applied onto a substrate to form a sheet having a basis weight of 50 g/m ² . The fibrous cellulose according to claim 1 or 2, wherein when a sheet is formed under the condition (a), the YI value of the sheet is 3.0 or less. The fibrous cellulose according to claim 1, wherein when the sheet is formed under the condition (a), the YI value of the sheet is 1.5 or less. A fibrous cellulose-containing composition containing the fibrous cellulose according to any one of claims 1 to 4. The fibrous cellulose-containing composition according to claim 5, which contains a solvent. The fibrous cellulose-containing composition according to claim 6, wherein the solvent is water and the total light transmittance is 80% or more when the solid content concentration is 0.2% by mass. A molded body formed from the fibrous cellulose according to any one of claims 1 to 4 or the fibrous cellulose-containing composition according to any one of claims 5 to 7. The molded product according to claim 8, which has a sheet shape. A fibrous cellulose having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, wherein the first dissociated acid amount in the fibrous cellulose is A1′ and the total dissociated acid amount in the fibrous cellulose is A2′. In this case, fibrous cellulose having A1′ of 1.35 mmol/g or more, A1′/A2′ value of 0.51 or more, and a degree of polymerization of 500 or more. A fibrous cellulose having a phosphite group or a substituent derived from a phosphite group, wherein the introduced amount of the phosphite group or a substituent derived from a phosphite group is 1.35 mmol/g or more. Fibrous cellulose having a degree of polymerization of 500 or more. Fibrous cellulose comprising a step of obtaining a cellulose raw material having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group by mixing a cellulose raw material with phosphorus oxo acid and/or a salt thereof and urea and/or a urea derivative. The manufacturing method of
In the step of obtaining a cellulose raw material having a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, the cellulose raw material is mixed with the phosphorus oxo acid and/or a salt thereof and the urea and/or a urea derivative, Including a plurality of one cycle steps of heating,
The decomposition rate of the urea and/or urea derivative in the one cycle step is 95% or less,
The method for producing fibrous cellulose, wherein A1/A2 is 0.51 or more, where A1 is the first dissociated acid amount in the fibrous cellulose and A2 is the total dissociated acid amount in the fibrous cellulose. The cellulose raw material is mixed with a compound having a phosphite group and/or a salt thereof and urea and/or a urea derivative to obtain a cellulose raw material having a phosphite group or a substituent derived from the phosphite group. A method for producing fibrous cellulose comprising steps,
In the step of obtaining the phosphorous acid group or a substituent cellulose raw material derived from a phosphorous acid group, the compound having a phosphorous acid group and/or a salt thereof, and the urea and/or urea derivative are added to the cellulose raw material. Including a plurality of one cycle steps of mixing and heating
The method for producing fibrous cellulose, wherein the decomposition rate of the urea and/or the urea derivative in the one-cycle step is 95% or less.